The problem of combining parts from different images to create a new superpositioned picture can be decomposed into the following steps: picture segmentation, positioning and scaling, light and spatial parameter matching and superposition of video image parts. As is well known, picture segmentation is a formidable problem.
Picture segmentation involves separating the picture part of interest (PPI) from other parts of an image. These latter parts are called the background (BG). The separated picture part of interest is then embedded into another picture, called the basic picture (BP).
At present, picture part of interest separation from a background is based on either chroma-key, luma-key or code key methods. However, these background keys generally require specific room, studio or light conditions or a priori information about the position of the PPI in the given frame. Therefore, their use is unsuitable for many applications where these standardized conditions can not be or are usually difficult to meet.
Much research has been carried out trying to improve picture segmentation. The following patents discuss various aspects of prior art methods in this field:
U.S. Pat. Nos. 3,961,133; 5,301,016; 5,491,517; 5,566,251; Japanese Patents 4-83480, 6-133221, 55-71363 and Great Britain Patent 1,503,612.
The following articles and books also deal with the subject:
Richard Brice, Multimedia and Virtual Reality Engineering, 1997, Newnes, 307 Lynn Conway and Charles J. Cohen, “Video Mirroring and Iconic Gestures: Enhancing Basic Videophones to Provide Visual Coaching and Visual Control”, IEEE Transactions On Consumer Electronics, vol. 44, No. 2, p. 388-397, May 1998;
Andrew G. Tescher, “Multimedia is the Message”, IEEE Signal Processing Magazine, vol. 16, No 1., pp. 44-54, January, 1999; and
Eugene Leonard, “Considerations Regarding The Use Of Digital Data To Generate Video Backgrounds”, SMPTE Journal, vol. 87, pp. 499-504, August 1978.